The desmosome is one of the key types of the cell junction-cytoskeleton complexes. Transmembrane desmosomal glycoproteins include the desmocollins (Dsc) and desmogleins (Dsg), both members of the cadherin family of cell adhesion molecules. The extracellular portion of these molecules are thought to mediate cell-cell interactions, and the intracellular region serves as an anchoring site for intermediate filaments. Loss of the epidermal integrity and blister formation is caused by autoantibodies directed against the desmogleins in pemphigus foliaceous and pemphigus vulgaris. The applicant's previous studies have led to the proposal that plakoglobin's (Pg) association with the intracellular domain of the desmosomal cadherins is one of the critical steps in desmosome assembly. In preliminary studies, it has been found that plakoglobin has three binding sites for cadherins that differ in their binding specificity. Studies are proposed to test the hypothesis that plakoglobin may function by coupling several cadherins and mediating their interaction with some unknown plasma membrane protein. In order to test this hypothesis, deletion mutants and site directed mutagenesis will be used to characterize the molecular determinants of Pg and the cadherins that are responsible for their interactions. A similar approach will be used to study the targeting of Pg to the desmosome. The role of phosphorylation in the regulation of these processes will also be determined. In addition, the effect of desmosome disruption on cell-cell adhesion will be studied in an in vitro skin equivalent utilizing HaCaT cells.